Electrical contact device



Nov. 3, 1936.

G. PRlKl-:L 2,059,488

'ELECTRICAL CONTACT DEVICE Filed Dec. 24, 1934 Patented. Nov. 3, 1936UNITED STATES PATENT OFFICE Application December 24, 1934, Serial No.759,040 In Rumania December 29, 1933 4 Claims.

This invention pertains to methods of igniting explosive charges inbore-holes, and is more particularly concerned with an electricalcontact device to be operated in conjunction with oil-well casingperforators using projectiles, such as are the subject of my co-pendingapplications Serial Nos. 656,607 and 736,473.

It has been customary up to now to ignite such charges either from thesurface of the earth, or by means of time contacts lowered into thewell.

The first method requires the use of long electrical conductors, and istherefore costly and unsafe, since the insulation of the conductorcannot long resist the` corroding action of the oil and the hardconditions of wear and tear in deep wells, the resulting short circuitsfrequently causing undesired ignitions of the charge. On the other hand,when time contacts are used, the moment of ignition must always beexactly determined in advance, and a premature ignition may occur incase of any trouble or delay in lowering the perforator orotherapparatus.

The purpose of this invention is to avoid these diiculties by providingfor the ignition circuit a contact device carried on the suspendingcable at a relatively short distance from the perforator, which contactmay be closed at any desired moment by means of a weight, or go-devil,dropped into the bore-hole.

The operation of this device will be understood from the followingdescription and drawing, wherein Fig. 1 diagrammatically shows thearrangement of the different pieces of apparatus used in perforating anoil-well casing, and Fig. 2 gives a vertical cross-sectional View of theelectrical contact device proper.

Referring to Fig. 1, a cable 20 supports a contact device 3 and anelectrical battery 1I, which is provided with a cover making itimpervious to the pressure and the corroding action of the well Viiuid.The battery is located at a short distance I9 below the contact devicewhile still farther down, a well-casing perforator E'is attached to thecable. The current in the circuit passes through an insulated wire frombattery 4 to a detonating cap in the perforator 5, from there throughthe suspending cable to the contact device 3, Where it is interrupted,and then farther through an insulated wire back to battery il.

Referring to Fig. 2, the contact device 3 consists of a tubular body Ewhich is rmly clamped to the suspending cable by means of a wedge 'E'and a screw cap 3. Guides or springs 9 keep the vbody of the devicecentered in the bore-hole.

The contact head I0 is arranged to move longitudinally over the tubularbody 6, and is held in its uppermost position by a spring or othercompressible means I I. Mounted sidewlse on the contact head Il! is aframe 22 supporting a contact pin I2, which is pressed to its lowermostposition by a spring I3.

Opposite the contact pin I2 is a contact I4,

held by a lateral projection I5 attached to theV tubular body 6. ContactI4 is insulated from the body of the device by a dielectric bushing I6,and is protected from the outside by a frangible plastic disc I'I.Contact I4 is connected with the battery by means of the insulated wireI8, while contact pin I2 is electrically connected to the body of thedevice.

The complete arrangement of parts shown on Fig. 1 and consisting of acasing perforator, an electrical battery, and a contact device islowered into the bore-hole on a cable.l When the casing perforatorreaches the desired depth, as calculated by the length of the cable paidout, a Weight is allowed to fall into the bore-hole, preferably bysliding along the suspension cable. The Weight presses down the contacthead Ill, the pin I2 perforates the rubber disc I'I and closes thecircuit formed by contact I4, the insulated wire I8, the battery 4,another insulated wire alongside of the portion 2| of the suspendingcable, the detonatng cap in the perforator 5, the suspending cable, andthe pin I2.

I claim as my invention:

1. An electrical contact device for a projectile well-casing perforatorsuspended by a cable, comprising a tubular body clamped to the cable, alateral projection on the tubular body carrying an insulated contact, acontact head sliding over V the tubular body, a contact pin mounted onthe contact head, a yielding means holding the contact head in itsuppermost position, said means being compressible and allowing thecontact pin to close with the insulated contact when a Weight droppedinto the well strikes the contact head.

2. In the device of claim l, a frangible disc protecting the insulatedcontact, said disc being -breakable by the contact pin when the contacthead moves down against the action of the yielding compressible means.

3. In the device of claim l, a plurality of spring guides around thetubular body of the contact device.

4. In combination with a projectile well-casing perforator suspended bya cable in a bore-hole, an electrical circuit comprising a detonator inthe head, saidcontacts closing' the circuit when the contact head-isdepressed against the action of the yieldable means by the impact of a,weight slidably dropped along the cable into the borehole.,

